403 Unit 1: MSK

In organs, Stroma is _ and Parenchyma is _

General supportive/connective tissue

Tissue relevant for specific organ function (e.g. hepatocytes)

LO: What are the 4 basic tissue types?

1. Epithelial

2. Connective

3. Muscle

4. Nervous

The deep part of epithelial cells are anchored to the same _

Basement membrane

LO: Do epithelial cells divide?

Yes, rapidly

O₂ reaches epithelial tissue via _

Diffusion (no direct blood supply)

Epithelium functions

1. Protection from harmful stimulus (e.g. skin protects from outside world)

2. Secretion (via glands)

3. Absorption (epithelial wall of GI tract)

4. Filtration (through kidney glomerulus)

LO: What factors are used to classify epithelia?

1. Shape

2. Number of layers

LO: Are epithelia vascular or avascular?

Avascular

Epithelial cell shapes

Squamous (flat), Cuboidal (cubes), Columnar (columns)

Epithelial layer types

1. Simple (1 layer)

2. Stratified (>1 layer)

Epithelial shape is classified by which layer?

The surface layer (apical)

Pseudostratified Epithelium

A single layer of epithelial cells attached to the same basement membrane that contains nuclei at different levels

Transitional Epithelium

Stretchy layers of stratified epithelium that can form a domed surface when subjected to distensive forces

LO: What are the functions of connective tissues?

1. Bind musculoskeletal structures (tendons/ligaments)

2. Provide structural support (bones and cartilage)

3. Protect organs (bones, cartilage, adipose)

4. Insulate body (adipose)

5. Transportation (blood)

LO: What cell types are found in connective tissues?

1. Fibroblasts (make fibers)

2. Macrophages (WBC’s which mount immune defense)

3. Mast cells (heparin and histamine production)

The connective tissue “matrix” is composed of _

Fibers (proteins) and Ground substance

_ connective tissues are not well vascularized

_ connective tissues are well vascularized

Cartilaginous, tendinous, and ligamentous

All other

LO: What are the 3 types of cartilage?

Hyaline, Fibrocartilage, Elastic

LO: What are the 3 types of loose connective tissue?

Areolar, Adipose, Reticular

LO: Rank the density of 1) Dense connective tissue, 2) Loose CT, 3) Liquid CT, 4) Bone CT, 5) Cartilage CT

1. Bone

2. Cartilage

3. Dense CT

4. Loose CT

5. Liquid CT

LO: Define tensile strength

Maximum force that a structure can withstand while being stretched (end to end)

LO: Define compressive strength

Maximum force that a structure can withstand while being compressed (end to end)

LO: Define shear strength

Maximum force that a structure can withstand while being pushed in opposite directions

Bone resistance ranking (shearing/tensile/compression):

1. _

2. _

3. _

1. Tensile

2. Compression

3. Shearing

Osseous Tissue is composed of _

Organic (collagen) and Inorganic (calcified mineral) components

Periosteum is composed of _ tissue

Dense, irregular connective

Ligaments and Tendons are composed of _ tissue

Dense connective

Red Bone Marrow function

Site of hemopoiesis (where RBC’s develop)

Yellow Bone Marrow function

Triglyceride storage in medullary cavities (hollow shaft of diaphysis)

Arteries carry blood _

Veins carry blood_

Away from the heart/Towards tissues

Towards the heart/Away from tissues

Nerves

Groups of axons bundled outside of CNS

• Which component of the skeletal system is important in hemopoiesis?

  • A. Arteries

  • B. Hyaline cartilage

  • C. Osseous tissue

  • D. Red bone marrow

  • E. Yellow bone marrow

D. Red bone marrow

Bone cell types

1. Osteogenic cells

2. Osteoblasts

3. Osteocytes

4. Osteoclasts

Osteogenic Cells

Stem cells of bone which can mature into osteoblasts when bone remodeling is necessary

Osteogenic cells can be found in _

The periosteum, Endosteum, and Nerovascular canals

Osteoblast Cells

“Bone-Building Cells” which 1) produce organic components of bone, 2) Initiate calcification, and 3) Contribute to hormonal regulation of resorption

Osteocytes

Mature bone cells which maintain bone metabolism via nutrient/waste exchange

Osteoclasts

“Bone resorbers” which break down bony ECM at the ruffled border via protons and lysosomal enzymes

When [blood calcium] is low, _ (bone cell type) should be up-regulated

When [blood calcium] is high, _ (bone cell type) should be up-regulated

Osteoclasts

Osteoblasts

Osteogenic cells are derived from _

Mesodermal mesoschyme

Progression of a bone cell throughout its lifetime

Mesenchyme —> Osteogenic Cell —> Osteoblast —> Osteocyte

Osteoclasts are formed via _

Fusion of monocytes

• In osteoporosis, bone resorption occurs at a higher pace than bone deposition. Which bone cells are outpacing the bone-building cells?

  • A. Osteoblasts

  • B. Osteoclasts

  • C. Osteocytes

  • D. Osteogenic cells

B. Osteoclasts

LO: List and describe the primary functions of the different types of bone cells

Osteogenic Cell: Differentiate into bone-building cells

Osteoblast: Build bone

Osteocyte: Maintain bony ECM

Osteoclast: Resorb bone

LO: Differentiate between the origins and development of the different types of bone cells.

• Osteogenic cells, Osteoblasts, Osteocytes share direct lineage from mesenchyme

• Osteoclasts form independently via monocyte fusion

LO: The organic component of osseous tissue is composed of _, which functions to _

Collagen, Provide flexibility and tensile strength to the bone (and an ECM framework)

LO: The inorganic component of osseous tissue is composed of _, which functions to _

Crystalized mineral salts (calcium, hydroxyapatite), Provide bone its hardened/calcified structure

Rough composition of bony ECM

• 30-40% organic components

• 45-55% inorganic components

• 15% water

• Which component of bone is primarily responsible for flexibility and tensile strength?

  • A. Calcium mineral salts

  • B. Collagen

  • C. Hydroxyapatite

  • D. Osteoclasts

B. Collagen

LO: Describe the location of compact and spongy bone in the skeletal system

Generally,

1. Compact bone forms the external layer of bones and most of the diaphysis shaft

2. Spongy bone forms short/flat/irregular bones and the epiphyses of long bones

LO: Identify the alternate names for compact & spongy bone.

Compact: “Cortical” or “Dense” Bone

Spongy: “Trabecular” or “Cancellous” Bone

Compact bones are organized into _

Osteons

Osteons

Concentric lamellae of mineralized bony ECM surrounding a central canal which contains neurovasculature and lymphatics

Perforating Canals/Volkmann’s Canals

Passages that transversely cross an osteon to connect neurovasculature from the periosteum to the central canals and medullary cavity

Circumferential Lamellae

Outer layer of osteons which connect directly to the periosteum and support appositional (“thickening”) growth

1

Circumferential Lamellae

2

Perforating/Volkmann Canal

3

Concentric Lamellae

Spongy bone is organized into _, determined by _

Trabeculae (not osteons), Lines of stress

• Which structures associated with compact bone directly surrounds a central canal?

  • A. Circumferential lamellae

  • B. Concentric lamellae

  • C. Perforating canals

  • D. Trabeculae

B. Concentric lamellae

LO: Explain the structural organization of compact bone, and identify the components of an osteon.

Compact bone is organized into repeating osteons with concentric lamellae, perforating canals, and circumferential lamellae

LO: Define and summarize the roles of perforating canals and circumferential lamellae.

Perforating Canals: Supply neurovasculature to medullary cavity and central canal

Circumferential Lamellae: Connect osteons to periosteum and support appositional growth

LO: Compare the organizational structure and function of spongy bone to compact.

Compact: Osteons with limited gaps for bone durability

Spongy: Trabeculae with large gaps to 1) hold marrow, 2) decrease brittleness, 3) decrease weight

Diaphysis

Body/shaft of a long bone containing mostly compact bony tissue

Epiphyses

Proximal and distal ends of long bones containing mostly spongy bone (with a compact bone cover)

Metaphysis

The region between a long bone’s epiphysis and diaphysis where growth plates reside

Growth plates are _ joints

Synchondrosis

Periosteum

A layer of dense irregular CT (outer) and cells (inner) which surround the external surface of a bone

Endosteum

The inner lining of the medullary cavity, bony canals, and spongy bones (wherever there is a hole/opening)

The articulating surface of epiphyses are covered by _

Hyaline cartilage

Medullary Cavity

The hollow space within a diaphysis where yellow bone marrow and vasculature reside

• Articular cartilage is typically located on what part of a long bone?

  • A. Diaphysis

  • B. Epiphysis

  • C. Medullary cavity

  • D. Metaphysis

  • E. Periosteum

B. Epiphysis

LO: List and describe the primary characteristics of the three major regions of a long bone.

1. Diaphysis (Long shaft made of compact bone)

2. Epiphysis (Proximal/distal ends made of spongy bone)

3. Metaphysis (Contain cartilaginous growth plates in region between diaphysis and epiphysis)

LO: Explain the role of the epiphyseal (growth) plate within the metaphysis.

Ossify during development/growth of long bones

LO: Summarize the composition and location of the periosteum, endosteum, articular cartilage, and medullary cavity.

1. Periosteum: Dense/irregular CT (outer) and cellular layer (inner) which wrap around bone

2. Endosteum: Single layer of cells which lines gaps in bone

3. Articular Cartilage: Cover epiphyses at joints with hyaline cartilage

4. Medullary Cavity: Hollow space in diaphyses containing yellow bone marrow and vasculature

LO: Define ossification and list four situations in which bone formation occurs.

The process by which bone forms during:

1. Initial bone formation

2. Bone growth

3. Bone remodeling

4. Fracture repair

Two methods of ossification

Intramembranous and Endochondral

Intramembranous Ossification

When bone forms directly within mesenchyme (mesenchyme —> bone)

_ bones undergo Intramembranous Ossification

Facial bones (including mandible and fontanels), Medial clavicle

Endochondral Ossification

Mesenchyme —> Hyaline cartilage —> Bone

_ bones undergo Endochondral Ossification

Most (non-facial or medial clavicular)

LO: Differentiate between intramembranous and endochondral ossification in terms of associated connective tissue and examples of bones formed through each method.

1. Intramembranous: Mesenchyme —> Bone (facial bones and medial clavicle)

2. Endochondral: Mesenchyme —> Hyaline Cartilage —> Bone (most other bones in the body)

Interstitial Growth

Growth of long bones endogenously from ossifying cartilage at epiphyseal plates

Appositional Growth

Growth of long bones exogenously via thickening of periosteum/endosteum

LO: Compare interstitial and appositional growth in terms of location and effects on bone structure.

Interstitial: Endogenous bone growth/lengthening at epiphyseal plates

Appositional Growth: Exogenous bone thickening along periosteum/endosteum

• The occipital bone of the skull forms via which type of ossification process?

  • A. Endochondral

  • B. Intramembranous

B. Intramembranous

_ bone undergoes remodeling faster than _ bone

Spongy, Compact

3 major factors affecting bone remodeling

1. Minerals (inorganic elements)

2. Vitamins (organic nutrients)

3. Hormones (regulation)

Minerals affecting bone remodeling

Calcium, Phosphorus, Magnesium, Fluoride, and more

Vitamins affecting bone remodeling

1. Vitamin A (osteoblast stimulation and collagen synthesis)

2. Vitamins C, K, and B₁₂ (osseous tissue protein synthesis)

3. Vitamin D (absorb calcium from GI tract to build osseous tissue)

Hormones affecting bone remodeling

1. hGH

2. Thyroid Hormone

3. Calcitonin

4. Parathyroid Hormone

5. Sex Hormones

6. Bonus: Calcitriol (active Vitamin D)

hGH effects on bone (4)

1. Stimulate osteoblasts

2. Promote cell division at epiphyseal plates

3. Increase necessary proteins

4. Promote synthesis of IGF’s

Thyroid Hormone effect on bone

Stimulate osteoblasts

Calcitonin effects on bone (2)

1. Promote blood calcium uptake

2. Inhibit osteoclasts

Parathyroid Hormone effects on bone (2)

1. Increase osteoclast activity (increase blood [Ca²⁺])

2. Stimulate calcitriol synthesis

Calcitriol

Active form of Vitamin D which increases absorption of calcium from GI tract

Sex Hormones effect on bone

Promote osteoblast activity during puberty

• If blood calcium levels are low, which hormone may be secreted in order to maintain homeostasis?

  • A. Calcitonin

  • B. Human growth hormone

  • C. Parathyroid hormone

  • D. Testosterone

C. Parathyroid hormone

LO: Explain the function of bone remodeling and identify differences in renewal rates between spongy and compact bone.

Bone remodeling is necessary to maintain stronger tissue along common lines of stress.

Rate_Spongy > Rate_Compact

LO: Explain the roles and effects of key minerals, vitamins, and hormones on bone growth and remodeling.

1. Minerals: Provide resources to build bone

2. Vitamins: Stimulate synthesis of proteins

3. Hormones: Regulate concentration of calcium in bones and blood